The present invention relates to low energy switches. The invention relates specifically to a mechanically actuated, power stealing, solid state switch providing a drop-in replacement for mechanical or electromechanical low energy switches.
Mechanical and/or electromechanical low energy switches, i.e., switches carrying low current at low voltage, designed for no-spark applications, e.g., 10 milliamperes (mA) at 5 volts (V) which may be used for small indicator lights, digital logic, or the like, suffer from corrosion build-up, oxidation, or contamination at their electrical contact points because there is not sufficient energy carried by the switch to create arcing or spark at the contacts in order to burn off the accumulation of contaminating material when the switch is actuated. Snap springs, armatures and like physical members are also subject to fatigue, assembly problems and packaging difficulties. Solid-state switches do not suffer from these problems.
Power stealing switches, which steal a small portion of power supplied to an actuated device and boost this stolen power to a voltage level sufficient to operate the power stealing switch, are known in certain contexts. The primary motivation for power stealing is to avoid rewiring of existing circuitry. In the art, there are power stealing switches, or parts thereof, in the context of thermostat control typically using twenty-four volt alternating current (AC) or ten-volt direct current (DC) at about 0.5 ampere. These switches steal power at the zero crossing points on the AC waveform. This opens the circuit for a short time and produces voltages that exceed the minimum digital logic low level, typically 0.5 volt. In the DC mode and with the switch on (ON) rather than off (OFF), the voltage is also greater than 0.5 volt. The related art has one or more voltage diode drops involved in the power stealing circuits and therefore does not allow operation in circuits with voltages as low as 1.5 volts.
It would therefore be desirable to provide a low power, solid state, two- or three-terminal switch with power stealing. Such a switch is further desirably connectable in any circuit configuration of current polarities and voltages ranging from 1.5 volts to 30 volts. A practical low power realization of a manually actuated, direct current, solid state switch of this type does not appear to be in the art.